If you tell me more about what you're looking for, I can help further:
Modern emulators (rAthena, Hercules) no longer trust the client. Your client says, "I have 0 delay!" The server responds, "No, my database says you have 1.5 seconds. I am ignoring your client request until 1.5 seconds pass." Result: You see the skill animation spamming on your screen, but the server deals damage only at the correct intervals. You lag out or get disconnected for "Packet Flooding." no delay grf ragnarok hot